Finally, anti-HIV microbicide research provides hope

Photo by bobbyramakantResearch into anti-HIV microbicides has finally produced a positive outcome—the microbicide gel PRO2000 achieved a 30% reduction in HIV transmission among women during recent clinical trials.

Women offered PRO2000 and condoms experienced 30% fewer HIV infections than women offered only condoms or condoms and a placebo gel, according to trial results presented by Protocol Chair Dr Salim S Abdool Karim, of the University of KwaZulu-Natal in Durban, South Africa.

Dr Karim presented the results at the 2009 Conference on Retroviruses and Opportunistic Infections (CROI). This multi-site clinical trial was known as HPTN 035, and was responsible for testing two candidate microbicides (PRO2000 and Buffer Gel). It was conducted by the US National Institute of Health (NIH) and was funded by the Microbicides Trial Network (MTN) in South Africa, Malawi, Zambia, Zimbabwe and the US.

The PRO2000 microbicide gel showed anti-HIV activity by reducing the HIV transmission risk among women by 30%, but the Buffer Gel was found to be ineffective.

The news of PRO2000's success is particularly encouraging to health advocates because microbicide research has faced so much disappointing news in the past decade, with different microbicide-candidate-products under research showing no positive anti-HIV effect in human trials.

According to WHO, microbicides are compounds that can be topically applied inside the vagina or rectum to protect against sexually transmitted infections (STIs) including HIV. They can be formulated as gels, creams, films, or suppositories. Microbicides may or may not have spermicidal activity (a contraceptive effect). At present, an effective microbicide is not available, and different candidate-microbicides are in various stages of research.

The Global Campaign for Microbicides (GCM), an advocacy organization that has been campaigning to expand women's HIV prevention options for over a decade, said in a press statement that adherence to the PRO2000 gel during the trials was as high as 81%. In another analysis that accounted for the time that women did not use contraceptives because they were pregnant, the study found PRO2000 to be 36% protective against HIV compared to the control arms.

"The results on PRO2000 are a ray of hope for women," observed Lori Heise, Director of the Global Campaign for Microbicides (GCM). "This is the first time that we have had human data actually showing that a vaginal gel can work to reduce infection. It's not a home run, but this "proof of concept" should invigorate the field"

Another effectiveness trial of PRO2000, conducted by the UK-funded Microbicide Development Programme (MDP), is currently in its final stages in South Africa, Tanzania, Uganda and Zambia. This trial—known as MDP 301—has enrolled over 9000 women, three times the number enrolled in HPTN 035.

“This second trial should help us refine our estimate of how effective PRO2000 actually is,” noted Dr. Samu Dube, GCM’s Africa Program Leader in the GCM press statement. “With three times the number of women, the MDP trial will yield an even more precise estimate of effectiveness. We will need such data before deciding whether it makes sense to move this product forward toward licensing and distribution.”

The development of microbicides is seen as a key to empowering women to protect themselves against HIV. Women are biologically more vulnerable to the transmission of STIs and many cultural and economic factors compound this vulnerability.

Millions of women live in societies that permit them no role in sexual decision-making, that condone male infidelity and assign the burden of shame and stigma associated with infectious diseases to women. Existing preventative strategies have largely failed to address this vulnerability, focusing on abstinence, mutual monogamy and male condom use, none of which are easily controlled by women.

Vaginal microbicides are also likely to fail until men understand and respect the need for women to protect themselves against HIV and other STIs. Not only do women need preventative options that they can choose to use freely but the gender inequalities that make it harder for women to insist on safer sex must be addressed.

For more information about microbicide development and trials, go to:
Global Campaign for Microbicides (GCM)
International Partnership for Microbicides (IPM)